Research directed by C. Daehler (UH Botany) with funding from the Kaulunani Urban Forestry Program and US Forest Service

Information on Risk Assessments
Original risk assessment

Corymbia citriodora; Eucalyptus citriodora; lemon-scented gum

Answer

1.01

Is the species highly domesticated?

y=-3, n=0

n

1.02

Has the species become naturalized where grown?

y=-1, n=-1

y

1.03

Does the species have weedy races?

y=-1, n=-1

n

2.01

Species suited to tropical or subtropical climate(s) (0-low; 1-intermediate; 2-high) – If island is primarily wet habitat, then substitute “wet tropical” for “tropical or subtropical”

See Append 2

2

2.02

Quality of climate match data (0-low; 1-intermediate; 2-high) see appendix 2

2

2.03

Broad climate suitability (environmental versatility)

y=1, n=0

y

2.04

Native or naturalized in regions with tropical or subtropical climates

y=1, n=0

y

2.05

Does the species have a history of repeated introductions outside its natural range? y=-2

?=-1, n=0

y

3.01

Naturalized beyond native range y = 1*multiplier (see Append 2), n= question 2.05

y

3.02

Garden/amenity/disturbance weed y = 1*multiplier (see Append 2)

n=0

n

3.03

Agricultural/forestry/horticultural weed y = 2*multiplier (see Append 2)

n=0

n

3.04

Environmental weed y = 2*multiplier (see Append 2)

n=0

y

3.05

Congeneric weed y = 1*multiplier (see Append 2)

n=0

n

4.01

Produces spines, thorns or burrs

y=1, n=0

n

4.02

Allelopathic

y=1, n=0

4.03

Parasitic

y=1, n=0

n

4.04

Unpalatable to grazing animals

y=1, n=-1

y

4.05

Toxic to animals

y=1, n=0

n

4.06

Host for recognized pests and pathogens

y=1, n=0

y

4.07

Causes allergies or is otherwise toxic to humans

y=1, n=0

n

4.08

Creates a fire hazard in natural ecosystems

y=1, n=0

4.09

Is a shade tolerant plant at some stage of its life cycle

y=1, n=0

n

4.1

Tolerates a wide range of soil conditions (or limestone conditions if not a volcanic island)

y=1, n=0

y

4.11

Climbing or smothering growth habit

y=1, n=0

n

4.12

Forms dense thickets

y=1, n=0

n

5.01

Aquatic

y=5, n=0

n

5.02

Grass

y=1, n=0

n

5.03

Nitrogen fixing woody plant

y=1, n=0

n

5.04

Geophyte (herbaceous with underground storage organs -- bulbs, corms, or tubers)

y=1, n=0

n

6.01

Evidence of substantial reproductive failure in native habitat

y=1, n=0

n

6.02

Produces viable seed.

y=1, n=-1

y

6.03

Hybridizes naturally

y=1, n=-1

y

6.04

Self-compatible or apomictic

y=1, n=-1

6.05

Requires specialist pollinators

y=-1, n=0

n

6.06

Reproduction by vegetative fragmentation

y=1, n=-1

n

6.07

Minimum generative time (years) 1 year = 1, 2 or 3 years = 0, 4+ years = -1

See left

3

7.01

Propagules likely to be dispersed unintentionally (plants growing in heavily trafficked areas)

y=1, n=-1

n

7.02

Propagules dispersed intentionally by people

y=1, n=-1

y

7.03

Propagules likely to disperse as a produce contaminant

y=1, n=-1

n

7.04

Propagules adapted to wind dispersal

y=1, n=-1

y

7.05

Propagules water dispersed

y=1, n=-1

n

7.06

Propagules bird dispersed

y=1, n=-1

n

7.07

Propagules dispersed by other animals (externally)

y=1, n=-1

n

7.08

Propagules survive passage through the gut

y=1, n=-1

n

8.01

Prolific seed production (>1000/m2)

y=1, n=-1

y

8.02

Evidence that a persistent propagule bank is formed (>1 yr)

y=1, n=-1

n

8.03

Well controlled by herbicides

y=-1, n=1

8.04

Tolerates, or benefits from, mutilation, cultivation, or fire

y=1, n=-1

y

8.05

Effective natural enemies present locally (e.g. introduced biocontrol agents)

y=-1, n=1

Total score:

9

Source

Notes

1.01

no evidence

1.02

1.03

no evidence

2.01

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

Review of natural distribution: The species is endemic to Queensland, Australia. The principal occurrence is in the region from north-west of Maryborough to north of Rockhampton, and west for up to 400 km, east of Clermont. There are also extensive stands inland from Mackay, west of Townsville, to the Atherton Tableland and the Windsor Tableland, and an inland occurrence north of Hughenden (Brooker and Kleinig, 1994). The latitudinal range of the northern area is 16.5- 20.0'S and that of the southern areas, 22.5'- 26S.

2.02

2.03

(1)CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International. (2)http://www.uog.edu/cals/PEOPLE/Pubs/Agrofors/Multspec.pdf

(1)Climatic requirements for E. citriodora derived from both its natural distribution and the climate of sites where the species has been successful as an exotic were estimated by Booth and Pryor (1991) as follows: mean annual temp. 17-28C, mean max. temp. hottest month 28-39C, mean min. temp. coldest month 8-22C, absolute min. temp. >-3C, mean annual rainfall 650-2500 mm of summer, uniform or winter incidence, and dry season (i.e. <40 mm/month) 0-7 months. The analysis showed that while the species occurs naturally in summer rainfall zones, it is also capable of growing successfully in winter rainfall dominant sites.
- Altitude range: 0 - 1800 m
- Mean annual rainfall: 650 - 2500 mm
- Rainfall regime: summer; winter; bimodal; uniform
- Dry season duration: 0 - 7 months
- Mean annual temperature: 17 - 28C
- Mean maximum temperature of hottest month: 28 - 39C
- Mean minimum temperature of coldest month: 8 - 22C
- Absolute minimum temperature: -3 - -3C (2)Elevation range in Pacific 0-200 m

2.04

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

Review of natural distribution: The species is endemic to Queensland, Australia. The principal occurrence is in the region from north-west of Maryborough to north of Rockhampton, and west for up to 400 km, east of Clermont. There are also extensive stands inland from Mackay, west of Townsville, to the Atherton Tableland and the Windsor Tableland, and an inland occurrence north of Hughenden (Brooker and Kleinig, 1994). The latitudinal range of the northern area is 16.5- 20.0'S and that of the southern areas, 22.5'- 26S.

2.05

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

Location of introductions: E. citriodora has been extensively planted as an ornamental tree in many regions of the world, and has been planted for commercial purposes in many countries in Africa and South America, and in China, Fiji, India, South America (especially Brazil, where 6 million trees were planted), and Sri Lanka

3.01

(1)http://pakistan.lead.org/CBD/chapter12.htm (2)http://www.zipworld.com.au/~aabr/info/weed_lists/weed02.html (3)http://www.tickey.co.za/rbhs/Trees%20at%20RBHS%20in%201997.pdf

(1)Not described as invasive in Pakistan (2)naturalized within Australia (3)Introduced, but not reported as naturalized within South Africa

3.02

no evidence

3.03

no evidence

3.04

(1)http://www.zipworld.com.au/~aabr/info/weed_lists/weed02.html (2)Randall, R. 2000. Garden Thugs. Plant Protection Quarterly (2)http://www.aildm.com.au/articles/plant%20info/weeds.htm

(1)Bushland Weeds of the Blue Mountains Region Australis; These lists were compiled by the Bushland Weeds Education Group, Sydney (An initiative of the Australian Association of Bush Regenerators). They have been prepared by practising Bush Regenerators to provide information about which popular garden plants have been found to be troublesome or destructive weeds in bushland of the Sydney region. [native to Australia] (2)Listed as an environmental weed of serious concern in Western Australia(2)Eucalyptus citriodora (syn. Corymbia citriodora), Lemon-scented Gum is invasive in north-east Victoria

3.05

Bacon, P. (Project coordinator) (1997) An electronic atlas of weeds and invasive species.Version 1.0 May 1997. (Based on the original work "Holm, L.; J.V. Puncho; J.P. Herberger & D.L. Plucknett (1979) A Geographical Atlas of World Weeds. John Wiley & Sons, Inc." )

no others recognized in Corymbia

4.01

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

no description of these traits

4.02

(1)Singh, P. N.; Gupta, S.; Azmi, S.; Singh, G. (192) Allelopathic effects of Eucalyptus citriodora Hook leaf leachate on germination and seedling growth of wheat, chickpea and toria. (ED: Tauro, P.; Narwal, S.S.) Proceedings. First National Symposium. Allelopathy in agroecosystems (agriculture & forestry), February 12-14, 1992, held at CCS Haryana Agricultural University, Hisar - 125004, India., 1992, pp.105-107, 10 ref. (2)http://bioenergy.ornl.gov/reports/euc-braz/eucal2a.html

(1)Aqueous extracts of air dried leaf litter of E. citriodora were tested in the laboratory for their inhibitory effects on the seed germination, seedling growth (shoot length and longest root length at 3 day old) and enzyme activity (glutamic-pyruvic transaminase [alanine aminotransferase], GPT, and glutamic-oxaloacetic transaminase [aspartate aminotransferase], GOT, at the end of the 45-h germination period) of 3 common rabi crops in north India: wheat, Triticum aestivum cv. RR-21; gram, Cicer arietinum cv. Avrodhi F; and mustard, Brassica campestris cv. Toria. Seed germination was inhibited in all 3 crops in the order wheat > mustard > gram. Shoot growth was most severely inhibited in gram, root growth in wheat, and both were inhibited to an intermediate degree in mustard. Amino acid contents and transaminase activities were measured only in wheat, where the reduction in germination with leachate treatment corresponded to high GPT and low GOT activities; high proportions of both free and bound amino acids

4.03

no evidence

4.04

(1)Couto, L.; Roath, R. L.; Betters, D. R.; Garcia, R.; Almeida, J. C. C. (1994) Cattle and sheep in eucalypt plantations: a silvopastoral alternative in Minas Gerais, Brazil. Agroforestry Systems, 1994, Vol.28, No.2, pp.173-185, 24 ref. (2)http://www.echonet.org/tropicalag/aztext/azch4mul.htm

(1)This study analyses the effects of cattle and sheep grazing in newly established eucalypt (Eucalyptus citriodora ) plantations at Dionísio, in Minas Gerais state, Brazil. The major problem in plantation establishment in this area is infestation by the grass Panicum maximum . The research was carried out using six separate treatment plots (3 ha) each having a different combination and number of animals (9 and 6 head of cattle alone, 10 head of sheep alone, and cattle and sheep at ratios of 9:10 and 6:10, respectively, and control (non-grazed) plots within the main plots). Eucalypt seedlings were planted in 1986 on harrowed and ploughed land, chemically treated (with dodecachlor) for ant control, fertilized with NPK +B + Zn, and manually weeded 30 and 60 days after planting. Livestock were introduced at the time when a third weeding would have been necessary (at 6 months old) when the trees were 2 m tall. Manual weedings were continued in the control plots. The results indicate that the silvopastoral approac

4.05

no evidence

4.06

(1)Dianese, J. C.; Moraes, T. S. de A.; Silva, A. R. (1984) Response of Eucalyptus species to field infection by Puccinia psidii. Plant Disease, 1984, Vol.68, No.4, pp.314-316, 14 ref. (2)http://www.actahort.org/books/452/452_8.htm

(1)Puccinia psidii attacks many forestry as well as agriculture species withi Myrtaceae. <http://www.up.ac.za/academic/fabi/tpcp/pamphlets/pdf/eucrust.pdf> (2)It is a pest of yellow guave, reducing yield 80-100%

4.07

no evidence

4.08

Burrows, G. E. (2002) Epicormic strand structure in Angophora , Eucalyptus and Lophostemon (Myrtaceae) - implications for fire resistance and recovery. New Phytologist, 2002, Vol.153, No.1, pp.111-131, many ref.

AB: Epicormic bud producing structures in the eucalypts, a large group of woody plants of considerable ecological, horticultural and silvicultural importance, are described. The outer portion of epicormic strands excised from the bark of large diameter stems of 18 Eucalyptus species (E. eximia , E. citriodora , E. calophylla , E. ficifolia , E. macrorhyncha , E. rossii , E. leucoxylon , E. melliodora , E. sideroxylon , E. caesia , E. lehmannii , E. macrocarpa , E. occidentalis , E. torquata , E. blakelyi , E. cinerea , E. globulus and E. nicholii ), two Angophora species (A. hispida and A. melanoxylon ) and Lophostemon confertus was examined anatomically in semithin sections. In the inner bark, each eucalypt strand usually possessed 5-12 radially orientated strips of tissue of meristematic appearance. The meristem strips were approx equal to 30-50 micro m high, 70-110 micro m wide and 2000-10 000 micro m long, with a lacuna above the meristem surface. Few buds or bud primordia were associated with the strand

4.09

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

"The ability of the species to compete with weeds is poor such that inadequate weed control may lead to the complete failure of a planting. E. citriodora is very light demanding, frequent and regular thinning is a prerequisite for healthy, vigorous plantations (Poynton RJ, 1979. Report to the Southern African Regional Commission for the Conservation and Utilization of the Soil (SARCCUS) on tree planting in southern Africa. Vol. 2. The eucalypts. 1979, xvi + 882 pp.; many pl., 2 maps (1 col.). Also ISBN 0-621-04763-5; 208 ref.)."

4.1

(1)CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International. (2)http://greencorridors.tripod.com/flora/flvara-l.htm

(1)E. citriodora is commonly found on rather poor gravelly soils, podzols and residual podzols of lateritic origin. Stands also occur on deep red loams, hard gravelly clay, and on soils derived from sandstone (Turnbull and Pryor, 1984). The soils are usually well drained. It occurs on rolling or undulating country, including plateaux and dry ridges. In dry regions and on sandy soils, it occurs in valley bottoms and along drainage lines (Boland et al., 1984).
- Soil texture: light; medium
- Soil drainage: free
- Soil reaction: acid
- Special soil tolerances: infertile
- Soil types: acid soils; lateritic soils; podzols; red soils; sandy soils (2)Adaptable to a large range of soil types.

4.11

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

"Medium-sized to large, straight stemmed tree, 25-40 m tall"

4.12

no evidence

5.01

terrestrial

5.02

tree; Myrtaceae

5.03

no evidence

5.04

tree

6.01

no evidence

6.02

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

"E. citriodora is usually propagated from seed. "

6.03

Cunha, R. A. da; Gurgel, J. T. do A.; Pisani, J. F. (1979) Comparative study of Eucalyptus citriodora and Eucalyptus maculata, and their natural hybrids. [FT: Estudo comparativo entre Eucalyptus citriodora Hook., Eucalyptus maculata Hook. e seus híbridos naturais.] IPEF, 1979, No.18, pp.121-132, 7 ref.

AB: A statistical analysis was made of morphological characters that could be used to distinguish E. citriodora, E. maculata, and their hybrids [in Brazil]. Leaf width and length were the most useful diagnostic characters.

6.04

Yeh, F. C.; Brune, A.; Cheliak, W. M.; Chipman, D. C. (1983) Mating system of Eucalyptus citriodora in a seed-production area. Canadian Journal of Forest Research, 1983, Vol.13, No.6, pp.1051-1055, 20 ref.

AB: Arrays of open-pollinated seeds were assayed for allozyme polymorphisms at 3 loci (Adh, Gdh, and Mdh-2 ) to obtain a quantitative estimate of outcrossing rate in a seed production area in Minas Gerais, Brazil. Rate of outcrossing varied among loci, but suggested overall that up to 14.7% of the seed might be derived from self-fertilization at the viable embryo stage. Such a level of partial self-fertilization, together with local variation in the mating system, yielded an observed average inbreeding coefficient of 0.205 for these loci in the progeny arrays. By contrast, the mature trees exhibited substantial excesses of heterozygotes (fixation index, F = -0.300), concordant with but not neccessarily supportive of earlier hypotheses that selection against homozygotes through the life cycle occurred in eucalypts. [selfed embryos don't survive?]

6.05

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

"Pollination is mainly by insects, but also by birds and small mammals."

6.06

no evidence

6.07

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

"Flowering usually starts within two years after planting, and seeds are produced abundantly by 5 years of age (Turnbull JW, Pryor LD, 1984. Choice of species and seed sources. In: Hillis WE, Brown AG, eds. Eucalypts for Wood Production. Sydney, Australia: CSIRO, Australia and Academic Press, 6-65.; Wasuwanich P, 1989. Phenological investigation of Australian tree species in field trials in Thailand. Unpublished report. Bangkok, Thailand: Royal Forest Department.)."

7.01

no evidence

7.02

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

Location of introductions: E. citriodora has been extensively planted as an ornamental tree in many regions of the world, and has been planted for commercial purposes in many countries in Africa and South America, and in China, Fiji, India, South America (especially Brazil, where 6 million trees were planted), and Sri Lanka

7.03

no evidence

7.04

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

"There are an average of 109,000 viable seed per kilogram of seed and chaff mix" [very small seeds]

7.05

no evidence

7.06

dry fruit

7.07

no evidence

7.08

no evidence of ingestion

8.01

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

"There are an average of 109,000 viable seed per kilogram of seed and chaff mix (Turnbull JW, Doran JC, 1987. Seed development and germination in the Myrtaceae. In: Langkamp PJ, ed. Germination of Australian native plant seed, 46-57, 186-198; 57 ref.). Seedlots vary in germination rate, but usually average 30-50%." [very small seeds]

8.02

CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International.

"No pre-sowing treatment is required. Rapid and complete germination is achieved under moist, warm (25-30C is optimal in the laboratory) conditions in the presence of light."

8.03

no evidence

8.04

(1)CAB International, (2000) Forestry Compendium Global Module. Wallingford, UK: CAB International. (2)http://pppis.fao.org/ (3)http://www.hort.purdue.edu/newcrop/duke_energy/Eucalyptus_citriodora.html

(1)Tolerates drought; fire; frost (2)The tree can be grown on coppice rotations of about 8 years. (3)Saplings areare lopped for the foliage; sucker shoots produce copious foliage.

8.05

no evidence